Toilet tank to bowl gasket

Wellworth toilet from 1950. Replaced the bolt washers without removing the tank and there is still a leak between the tank and bowl so I am assuming it needs a tank to bowel gasket.

Would anyone happen to know what size gasket I will need? I will bring the old one to the plumbing supply store but it would be nice if i could buy the part ahead of time.

Also, the toilet still has the original flush valve in it (the fill valve has been replaced with a fluidmaster 400a). While I had the tank off I was going to attempt to replace the gasket underneath the valve. Would the gasket still be available or should I just get a whole new flush valve assembly. I hate replacing the old stuff, especially if it is working fine and is probably built better than the new stuff...


You can get easily find a proper flush valve gasket. Many of us prefer to nut the tank bolt with a nut and washer directly against the bottom of the tank, then put the bolt down through the bowl and nut that. You can really snug up that nut at the bottom of the tank and get a much better squeeze than you can on the nut under the bowl flange.